I wouldn't recommend a 55 gallon. I'd say a 30 gallon at most for a small group of females.
Such a large terrarium makes it hard for them to find food, water or heat.
80-90F is perfect for them.
You could think with a large tank you could just have half the tank heated, but that's not very healthy, as I'm sure you know they're cold blooded and can't regulate their own heat by heating up or sweating. Too much heat and they'd overheat.
Lighting as in heat lamps is not necessary, they're nocturnal, and don't bask.
Lighting in general is better for them, giving them a natural day and night cycle gives them a healthy sleep schedule. Mine don't really go by a sleep schedule, they just sleep whenever and they're fine, even though they have a relatively normal light cycle around them.
I recommend a heat pad under their designated warm hide.
A tank that's always hot isn't too healthy either. They get hot and stressed when they can't move to a cooler side to cool down.
for their cooler temps, 75-80 is fine... wet towels on the lid help cool it down with the evaporation.
If you want a lizard that can deal with the heat and the large tank, go with a bearded dragon. Just as nice, just as cool, likes warm temps and basks all day. HOWEVER they themselves can be a bit expensive, along with lighting and food.
as for food I recommend breeding your own... Dubia roaches or superworms are good.
Dubia roaches can't fly, and can't breed without tropical environments.
They also don't smell like crickets and have more nutrition.
crickets smell really bad, and mealworm shells (unlike superworms) ar hard to digest for the dragons.
Also superworms bite, so be careful...